Radio direction finder



Sept. 28, 1948. T. H. CLARK l RADIO DIRECTION FINDER Filed June' 50, 1945 MME? 'Patented Sept. 28, 1948 RADIO DIRECTION FINDER Trevor H. Clark, New York, N. Y., assigner to Federal Telephone and Radio Corporation, New York, N. Y., a corporation ofDelaware Application June 30, 1945. Serial No. 602,451

This invention relates to an indicating means for selecting a given one of a series of energy impulses. More particularly it deals with a means for correlating a movable dial with the oscillorph patterns on the screen of a cathode ray It is an object of this invention to simplify the reading of an oscillograph indicator.

Another object is to increase the accuracy of the visual indication, on the screen of a cathode ray tube.

Another object is to prevent errors in reading the indications on the screen of the cathode ray tube.

Another object is to simplify and to reduce the error in reading of a radio direction iin-der, comprising a cathode ray tube, and particularly a radio direction finder of the amplitude comparison type.

Stili another object is to read the actual direction of an' incoming wave accurately and directly on the dial of a radio direction finder.

Other objects of this invention will appear from time to time in the description which follows:

This invention comprises an indicating means which may be used in conjunction with the viewing screen of a cathode ray tube in order to directly correlate the pattern of the screen with the visual figures on the indicating means. The oscillograph pattern on the screen is produced by energy impulses through a switching means and a sweep circuit synchronized with that switching means. This switching means couples the cathode ray tube repeatedly and successively with a series of contacts any one or more of which are capable of transmitting energy for indication on the tube screen. The indicating means is provided with a dial which is divided into zones corresponding with each one of the series of contacts successively coupled by the switching means; so that when one or more of the contacts transmits energy to produce a pattern on the screen, the proper correspon-ding Zone of the indicating means may be selected to give a direct reading. A second indicating means cooperating with a corresponding zone of the :ilrst indicating means may be movably connected in the circuit from the contacts to the cathode ray tube to compare the patterns produced in two adjacent zones on the screen of the tube.

A better understanding of this invention and the objects and features thereof may be had by reference to a particular description of an ein? bcdiment thereof made with reference to the ac- 3 Claims. (Cl. 343-120) companying drawing. This drawing is a schematic circuit diagram, partly in block, of an amplitude comparison type of a direction finder circuit embodying the indicating means of this invention.

Referring to the drawing the area about the receiver-may be divided into quadrants I-2; 2 3; 3-6 and vli--L An incoming radio signal 5 in quadrant I--Z is picked up partly by antenna 6 and partly by antenna 1 of the group of unidirectional antennas 6, l, 8, and 9 positioned at the four directions of the compass. 'I'hese antennas are shielded from each othery so thatl at the most two antennas will respond to one signal coming from one direction. Each antenna may be directly connected to an electronic switching means I0. The antenna circuits are separately and successively and repeatedly energized by the commutator arm II rotated by a suitable motor I2 through shaft I3. Direct current is applied to the arm II through line I4 from direct current generator I5. By this means, only one antenna 'circuit is connected to the receiver I6 at onetime. A more complete understanding of this type of directionfndcr comparison system may be had by reference to the copendlng application of N. Marchand, Ser. No. 565,142, filed November 25, 1944, now Patent No. 2,448,041, which issued August 31, 1948.

'I'he motor I2 should be rotated at a speed suilicient to produce from each one of the contacts contacted by the arm II an oscillograph pattern that is persistent to vision. For example, a speed of about 20 R. P. M. has been found suflicient although faster speeds may be employed if desired.

Since no two oppositely positioned antennas can receive an impulse from one direction at the same time, the circuits of opposite antennas may be coupled for comparison of impulses from adjacent antennas. 'I'his is accomplished by passing the circuit from receiver IB through line I1 to a commutator having arm I8 mounted on shaft vI3 and rotated in synchronism with arm II by motor I2.

In a direction finder of this type, wherein the direction is determined by comparing the amplitude of the signal from two adjacent antennas, a pair of coupled attenuators I9 and 20 are positioned in each one of the pair of circuits from commutator at i8. The impulses from antennas 6 and 8 pass through. attenuator I9, while impulses from antennas l and 9 passthrough attenuator 20. 'I'hese attenuators are both coupled together through shaft 2i such that when one attenuator is at its maximum, the other one is at its minimum control position. Shaft 2i is directly connected to the center manual knob 22 (on the instrument panel 23) and to the pointer 2d winch cooperates with the dial -31 described later.

The impulses, after passing through their respective attenuators, pass through line 25 and are applied vertically across the lcathode ray tube 26. The impulse from the signal wave corresponds here to full line waves 21 and 28 shown on the screen of the cathode ray tube 26.

The sweep circuit for the tube 26 is synchronized through the commutator arm 29 connected to shaft I3 together with arms il and I8. Direct current from the generator I5 is coupled through line 30 to arm 29 to separately energize the four contacts 3l, 32, 33, and 3d, each one of which may be connected to the sweep circuit generator 35. This generator 35 is shown in the drawing to spread the impulses applied over line 25 across the tube horizontally at a speed so that one sweep equals one revolution of the motor I2 or the arm II. This divides the horizontal sweep line into four equal zones (1), (2), (3), (4), corresponding to each one of the four unidirectional antennas E, 1, 9 and 9 respectively.

Since the northern component of the signal 5 is greater than the eastern component of the signal 5, the amplitude of the signal received by antenna 6 is greater than that received by antenna 1; and, correspondingly, the amplitude of the wave pattern in zone (l) ofthe cathode ray tube 26 is greater than that in zone (2), (see waves 21 and 28). In order to determine the exact direction of the signal 5, the amplitude of the impulses in the respective circuits of the two antennas` are attenuated to form two waves of equal amplitude (see dotted line wave 36) by turning the knob 22 to operate the attenuators I9 and 20. This turns the pointer 24 also connected to the knob 22, to a denite position with respect to the dial 31, thus indicating thereon the exact angle in degrees of the incoming signal.

If the signal were coming in overA antennas 1 and 8 (or in quadrant 2 3) instead of over antennas 6 and 1, the oscillograph pattern would occur in zones (2) and (3) of the tube screen, instead of zone (1) and (2). In quadrants 2 3 and 4 I the attenuators I9 and 20 are coupled to give impulses in the reverse sequence to those impulses received from signals in quadrants I 2 and 3 4. This causes the adjustment of knob 22 for signals from quadrants 2 3 or 4 I to be in the opposite directionfrom a corresponding adjustment for signals from quadrants I 2 or 3 4. In order to prevent confusion, the angular degrees on dial 31 in each quadrant are alternately numbered; quadrants I 2 and 3 4 being numbered in a clockwise direction, and quadrants 2 3 and 4 I being numbered in a ycounterclockwise direction. Furthermore to prevent confusion, dial 31 may be rotated by outer knob 38 and may be masked so that only one quadrant of the dial` 31 is made visible at one time through the aperture 39 in the front panel 23 of the apparatus.

In order to know which quadrant to place in front of the aperture 39, the quadrants on the dial and the zones on the tube may be similarly numbered (as shown (l) (2), (3), (4) Thus, before the attenuator knob 22 is adjusted, the dial must be turned by large knob 38 so that the numbers for the zones showing patterns on the tube screen are the same as numbers on the visible quadrant o! the dial 31.

Instead of using marks on the tube screen zones and the dial quadrants, the large knob 33 may be connected through shaft 40 to switch 4I which operates any adjacent pair of the series ofv lights d2, 43, 44 and 45, located directly under and corresponding to zones (1). (2) (3) and (4) respectively, on the screen of the cathode ray tube 28. Thus, to make sure that the proper quadrant or zone will appear in the opening 31, knob 38 is rotated until the lights are lighted under the two zones of cathode ray tube 29 which show patterns. By this visual means direct reading of the angle of the incoming wave on the correct quadrant oi' dial 31 maybeobtained.

Another form of quadrant indication of this invention is. included by connecting the shaft 40 directly to a switch 46 which changes the phase or initiation timing oi the synchronism o! the sweep circuit 35 of the tube 28 over contacts 3l and 34 so that a pattern from a signal in any quadrant may be always placed in the same two zones; for example. zones (l) and (2). Thus, when knob 38 is turned so that the pattern is always shown in zones (1) and (2), the proper corresponding quadrant of the dial 31 is visible through the aperture 33. The lights 42 to 43 inclusive are simultaneously switched to indicate the different quadrants. the series of lights 42 to 43 inclusive, and switch 6I as well as the markings on the tube screen and dial 31 may be dispensed with if'desired.

This latter modliication involving switch 46 without the lamp permits a further modiflcation' wherein it is unnecessary to provide a sweep circuit of such a length as to show all four quadrants at one time on the tube screen. Since the pattern on the screen is always turned to a given'position, no more than two zones need to be seen at one time on the screen. Thus, the sweep circuit for the screen may be made only two zones wide by a suitable means (not shown) coupled in the sweep l pattern to be doubled and thereby increases the accuracy with which it can `be attenuated. This in turn increases the accuracy of the direction reading on dial 31, V

While the above is a speclilc application oi this invention it is clear that many modifications will appear to those skilled in the art. For example, instead of -using the motor I2 and the contact switches, electronic or other lswitching means may be employed to synchronize and control the impulses to the respective contacts to switch arm I3.

Instead o! using a deection control for producing indication on the osciilograph screen, other known methods such as control of beam intensity may be used if desired.. Moreover. other types of scanning indicators may be used in place of the oscillograph indicator. It should be understood that various types of unidirectional antennas may be provided, and that any number of antennas that is a multiple of two may be employed, if desired.

In view of the above, this invention can be applied to many other types of control apparatus involving recordation, indication and/or correlation of a series o! impulses which are cyclically repeated. Thus, the above example shown in the drawings and described in the specification is merely by wayl of illustration and not to be considered a limitation of this invention as defined l When using switch 43- circuit. This enablesthe size of the,

couple each antenna independently and successively to said receiver, a variable attenuation means for each oppositely paired antenna circuits and coupled with said switching means for coupling the output of said receiver to one set of deiiection means of said tubes, said tube having a screen divided into at least two adjacent zones corresponding to at least two adjacent antennas, a sweep circuit means having its output coupled to another set of deection means of` said tube and synchronized with said switching means an azimuth dial having sectors corresponding to each of said antennas to select that sector on said dial corresponding with a given zone on said screen oi said tube, and means for varying said attenuation means and said azimuth dial simultaneously to obtain an indication of said selected sector of said dial of the direction of radian energy received by said antennas.

2. In a radio signal direction nder comprising at least four oppositely paired shielded unidirectional antennas, a switching means to couple each antenna independently and successively to a receiver, a variable attenuation means for each oppositely paired antenna circuits synchronously connected to said receiver by said switching means, a cathode ray tube having a screen divided into at least two adjacent zones corresponding to at least two adjacent antennas; the improvement comprising an adjustable sweep circuit for said tube synchronized with said switching means, an

adjustable azimuth dial having sectors corresponding to each of said antennas, means for adjusting said sweep circuit means to indicate energy from a given one or'more of said antennas on said screen of said tube, said latter means being directly connected to select that sector on said dial corresponding with the given antenna for varying said attenuation means and said energy being indicated on said screen, and means 40 Number 6 'azimuth dial simultaneously to indicate the actual direction on said selected sector o! said dial of a radio signal imparting energy to said adjacent antennas.

3. In a direction nder comprising a receiver, a cathode ray tube, positioned antennas to receive signalsl approaching from different quadrants. means for successively coupling combined ones oi said antennas to said receiver, switching means in the output of said receiver operated synchronously with the successive coupling means to apply the output energy received from said combined antennas to diierent lines, a variable atsaid lines in parallel to said indicator to control a characteristic of said beam in accordance with the amplitude of the received signals, an azimuth dial having sectors corresponding to each of said quadrants, and means for selecting a given sector, means for sweeping the beam of said oscilloscope across the screen thereof in synchronism with the coupling oi' said antennas, and in accordance with said selected sector, means for varying an indicator of said azimuth dial in accordance with the balancing of said attenuating means to indicate a bearing direction of radiant energy received in said given sector.

TREVOR H. CLARK.

vincarnations CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Jeii'cock Sept. 3. 1940 Ripley May 26, 1942 Christaldi Aug. 8, 1944 Roberts Jan. 2, 1945 

